International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-6 Issue-6, August 2017 Studies of Unodped Glycine, Cesium Chloride Doped Glycine and Rubidium Chloride Doped Glycine Crystals P. Manimekalai, P. Selvarajan glycine which have been synthesized to grow single crystals Abstract- Glycine is one of the simplest amino acid that has no and characterize them [11-14]. asymmetric carbon atom and is optically inactive. It is mixed with The effect of additives has been investigated on the other organic or inorganic salts and acids to obtain new crystal morphology and polymorphism of glycine and it was complexes and these complexes have improved chemical stability, explained that the crystallization of the least stable form β and thermal, optical, mechanical, electrical, linear and nonlinear γ optical properties. Many glycine based crystals are known to be the stable form from aqueous solution correlated with having interesting properties and in this work, cesium chloride conditions that had inhibitory effects on the dimer formation, and rubidium chloride are separately added in small amounts into thus inhibiting the spontaneous nucleation of the α-form [15]. the lattice of glycine crystals to get the doped samples for the Profio et al. studied the selective nucleation of α− and research work. Single crystals of undoped, cesium chloride doped γ− forms of glycine by using microporous membranes [16]. and rubidium chloride doped glycine were grown by solution Recently, various studies on potassium nitrate doped glycine method and grown crystals were analyzed by various characterization techniques. Solubility was measured for the crystals were reported in the literature [17]. samples. XRD study was carried out to find the crystal structure and hardness study was done on the crystals to find the II. EXPERIMENTAL mechanical strength. Second harmonic generation studies were carried out to find SHG efficiency. Density and structural A. Growing Crystals characterization was performed for the samples. AR grade chemicals such as glycine, cesium chloride and Photoconductivity studies were carried out for the samples and the rubidium chloride were purchased commercially from Merck results are discussed. India. Double distilled water was prepared using the double Index terms: Doping, glycine, crystal growth, distillation plant and it was used for synthesis and growth of characterization, XRD, hardness crystals. Three samples viz. (i) undoped glycine, (ii) cesium chloride doped glycine and rubidium chloride doped glycine I. INTRODUCTION were prepared here. Single crystals of these samples were grown by solution method with slow evaporation technique. Many researchers are actively involved in using amino To get the doped samples, 2 mole% of cesium chloride and acids like glycine, L-alanine, L-arginine, L-histidine, rubidium chloride were added separately into glycine. L-threonine, L-proline etc to prepare novel second-order and Saturated solutions of undoped glycine, rubidium chloride third-order NLO crystals for usage in laser, optical and doped glycine (RCG) and cesium chloride doped glycine photonic technologies[1-5]. Among amino acids, glycine has (CCG) were prepared in three different beakers using the the non-chiral zwitterionic form and it crystallizes in six double distilled water as the solvent. The prepared solutions ’ different polymeric forms viz. α, β, γ, δ, ε and β - forms. were stirred well for about 3 hours using a hot plate magnetic α-glycine has no asymmetric carbon atom and is optically stirrer and were filtered. The filtered solutions were taken in inactive. It has been reported that glycine combines with three different growth vessels and covered with perforated sulpuric acid, nitric acid, calcium chloride, calcium nitrate, sheets for slow evaporation. Quality crystals were harvested barium chloride, silver nitrate, phosphoric acid, lithium after a growth period of 30 days and the photograph of the sulfate, sodium nitrate, hydrochloric acid etc to form useful grown crystals is shown in the figure 1. single crystals [6-10]. Complexes of glycine with inorganic salts which crystallizes in non-centrosymmetric space group have been reported to be promising materials for SHG. Glycine silver nitrate, glycine hydrogen nitrate, glycine hydrogen phosphate, glycine lithium sulphate, glycine zinc sulphate, glycine zinc chloride, diglycine manganese chloride and triglycine fluoroberrylate are some of the complexes of Revised Version Manuscript Received on July 14, 2017. P. Manimelalai , Department of Physics, Christ The King Polytechnic College, Othakkalmandapam, Coimbatore-641032, (Tamil Nadu), India. E-mail: [email protected] P. Selvarajan , Department of Physics, Aditanar College of Arts and Science, Tiruchendur-628216 (Tamil Nadu), India, E-mail: [email protected] Published By: Blue Eyes Intelligence Engineering 78 & Sciences Publication Pvt. Ltd. Studies of Unodped Glycine, Cesium Chloride Doped Glycine and Rubidium Chloride Doped Glycine Crystals Fig.1: Grown crystals of (a) glycine, (b) cesium chloride doped glycine (CCG) and (c) rubidium chloride doped glycine (RCG) B. Characterization techniques Single crystal XRD data of the samples were obtained Fig.2: Solubility curves for undoped glycine, cesium using ENRAF CAD-4 X-ray diffractometer with MoK α chloride doped glycine and rubidium chloride doped (λ=0.71069 Å) radiation. The powder XRD pattern of the glycine crystals sample was recorded on a microprocessor controlled X-ray diffractometer using nickel filtered CuK α radiation. The B. Nucleation kinetic studies microhardness studies for the grown crystals were carried out Nucleation kinetic studies are necessary to get the using a SHIMADZU HMV-2000 microhardness tester fitted optimized growth parameters and these parameters can be with a Vickers diamond pyramid intender. To confirm the used to grow good quality crystals by slow evaporation and nonlinear optical property, Kurtz and Perry powder SHG test slow cooling techniques. Initially the induction period was was carried out for the grown crystal using Nd:YAG measured at different values of supersaturation ratio for the Q-switched laser which emits the first harmonic output of samples and using these values the critical nucleation 1064 nm. Density was measured by floatation method. parameters were determined. The time interval in which the Vickers hardness tester was used to measure the first sparkling particle is formed in the supersaturated solution microhardness of the samples. Photoconductivity studies have is called as the induction period. The induction period was been carried out using a photoconductivity set-up with a measured by isothermal method at room temperature (30 oC) Keithley 485 picoammeter at room temperature. at different supersaturation ratios (S) viz. 1.2, 1.25, 1.3, 1.35 and 1.4. A constant temperature bath, hot plate magnetic III. RESULTS AND DISCUSSIONS stirrer and a nucleation cell (corning glass beaker) were used for measuring the induction period. A powerful lamp was also A. Solubility Measurement used for observing the formation of the nucleation in the Solubility is a measure of the chemical potential of solid in supersaturated solution. Supersaturated aqueous solution of the saturated solution. The growth rate of a crystal depends on the sample was taken in the nucleation cell and when the its solubility and temperature. Solvent and solubility factor nucleation occurs in the cell, it grows quickly and a bright define supersaturation which is the driving force for the rate sparkling particle forms in the nucleation cell and time of crystal growth. Hence for a material to grow as a crystal, interval in which the first sparkling particle is formed in the determination of its solubility in a particular solvent is an solution was measured as the induction period. This essential criterion. The solubility of the samples was procedure was followed for measuring the values of induction determined at different temperatures such as 30, 35, 40, 45, period at the different supersaturation ratios. The variations of 50, 60 oC. A constant volume of 50 ml of the saturated solution induction period with supersaturation ratio for the samples are was used in this experiment. The measurement was performed provided in the figure 3. The results show that the induction by dissolving the sample in water in an airtight container period decreases with supersaturation ratio for all the three maintained at a constant temperature with continuous stirring. samples. When rubidium chloride and cesium chloride were The solution was constantly stirred for 2 h using magnetic added as the dopants into glycine, the induction period is stirrer for homogenization. Then solubility was determined by noticed to be decreasing. The classical homogeneous gravimetrical method and the variation of solubility with the nucleation theory was adopted to determine the critical temperature for the grown crystals is presented in the figure 2. nucleation parameters and the formulae used for calculating The results indicate that the solubility increases with increase the critical nucleation parameters are given in the reference of temperature for the samples. It is observed that when [18]. The obtained values of Gibbs free energy change, cesium chloride and rubidium chloride were added as the critical radius, number of molecules in the critical nucleus and dopants, the solubility increases which indicates that the nucleation rate are given